Haemophilus influenzae (Hi) is a gram-negative coccobacillus of the family Pasturellaceae responsible for several, often life-threatening, respiratory infections including meningitis. Its sole niche is the human respiratory tract, where it can be asymptomatically carried.
Hi is serotyped based on 6 capsule types (designated a-f) or it can be non-typeable (NT). Hi is the etiologic agent of a wide variety of diseases, ranging from otitis media to sinusitis to septicemia to chronic obstructive pulmonary disease. The pathogenicity of Hi depends on the presence or absence of a capsule and the specific capsule type. The Haemophilus influenza serotype b (Hib) is responsible for most Hi disease in young children and for as much as 50% of adult diseases. Hib is the target of vaccines administered to infants. Widespread vaccination programs dramatically decreased the prevalence of disease in all countries employing the vaccines. Non-typeable Hi has, thus, become the most prevalent cause of Hi related infections in the United States.
Common techniques employed for the identification of Hi serotypes include slide agglutination serotyping (SAST) and the polymerase chain reaction (PCR). The reading and scoring of SAST results are subjective, and can be difficult to interpret if an agglutination reaction is weak or if there is variability in the sensitivity or specificity of commercially available serotyping reagents.
The change in prevalence of disease causing primary serotypes underscores the need for continued monitoring to detect serotype replacement or identify vaccine failure. Thus, there is a need for compositions and methods useful in improving the detection and serotyping of Haemophilus influenzae. 